The present invention relates to an ink-expelling restoring device and method for restoring, when ink-expelling failure occurs, the ink-expelling capability of an ink jet printer of the type in which a pressure generating device applies pressure to the ink in an ink chamber to discharge a stream of ink droplets through the opening of a nozzle from the ink chamber.
In an ink jet printer, a piezoelectric element and a bubble generating device, which are located between an ink tank and the opening of a nozzle, apply a pressure pulse to the ink in the ink tank to expelling a stream of ink droplets toward a recording media, thereby recording dots on the recording medium. The diameter of the nozzle opening is extremely small, e.g., several tens of microns, so as to obtain a good resolution of an image recorded with patterns of such dots. However, if dust, ink residue, etc., sticks to the nozzle opening, the picture quality is remarkably deteriorated.
To avoid the deterioration of the picture quality, the conventional printer has an ink-expelling capability restoring function. In the ink-expelling restoring process, after continuous printing has been carried out for a certain period of time, the printing operation is brought to a stop and a capping member is applied to the front face of the recording head to apply a negative pressure thereto and to forcibly discharge the ink therefrom.
To ensure complete cleaning of the recording head, the restoring operation is performed in combination with both a wiping operation and a flushing operation. The wiping operation is employed to wipe dust from the front face of the recording head by rubbing with a resilient plate piece. The flushing operation is to flush the nozzle with ink for restoring the meniscus that was destroyed by the wiping operation.
When the ink in the ink tank is used up during the ink-expelling restoring operation, bubbles tend to enter the ink supply path and the recording head. Also, ink in the ink supply path can solidify, making it difficult to remove the ink therefrom.